UNIVERSITY    OF    CALIFORNIA 

COLLEGE    OF    AGRICULTURE 
AGRICULTURAL   EXPERIMENT   STATION 

.     CIRCULAR  No.  236 
April,  1922 

THE  COMMON  HAWKS  AND  OWLS  OF  CALIFORNIA 
FROM  THE  STANDPOINT  OF  THE  RANCHER 

By  JOSEPH  DIXON 

Contribution  from  the  Museum  of  Vertebrate  Zoology  of  the  University  of  California 


The  fi business  part"  of  the  barn  owl.     This  is  the  best  gopher  trap 
that  has  ever  been  invented. 


It  is  the  purpose  of  this  bulletin  to  point  out  some  of  the  characters 
and  habits  by  which  the  rancher  may  distinguish  his  friends  from  his 
foes  among  the  common  hawks  and  owls  of  this  state. 

Twenty  kinds  of  hawks  and, as  many  kinds  of  owls  are  known  to 
occur  in  California.  To  describe  all  of  these  forty  forms  in  detail 
would  confuse  rather  than  help  most  people.  Therefore  groups  of 
hawks  and  owls,  rather  than  species,  and,  further,  only  those  of  prime 
economic  importance  are  dealt  with  at  length  in  this  study.  All  the 
photographs  are  from  living  individuals. 


Z  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  people  of  the  state  of  California  spend  upwards  of  $50,000 
each  year  in  trying  to  control  rodent  pests.  The  cost  and  necessity 
of  this  work  have  increased  rather  than  decreased  as  the  years  have 
gone  by,  and  some  persons  are  beginning  to  realize  that  this  condition 
has  been  brought  about  in  large  measure  by  the  killing  off  of  the 
natural  enemies  of  our  two  most  destructive  rodent  pests,  the  Califor- 
nia ground  squirrel  and  the  pocket  gopher.  Some  of  these  age-long 
natural  enemies  of  the  ground  squirrel  and  gopher  are :  hawks,  eagles, 
owls,  coyotes,  badgers,  weasels,  wildcats,  and  gopher  snakes.  In  de- 
stroying beneficial  species  of  hawks  and  owls,  the  rancher  is  often 
unwittingly  ' '  losing  dollars  trying  to  save  cents. ' '  Unlike  strychnine, 
these  birds  do  not  endanger  human  life,  and,  better  than  traps,  they 
are  set  all  the  time.  In  any  case,  it  costs  little  to  let  them  go  about 
their  business  of  catching  gophers  and  squirrels  in  their  natural  way. 

Hawks  and  owls  have  all  too  often  been  considered  bird  outlaws, 
and  bounties  have  been  placed  on  their  heads.  The  feeling  against 
these  birds  as  a  class  is  due  to  the  depredations  of  a  few  harmful 
species.  The  fact  is  that  the  large  majority  of  our  hawks  and  owls 
are  decidedly  beneficial.  Through  indiscriminate  shooting  the  inno- 
cent many  suffer  with  the  guilty  few.  Farmers  and  ranchers  who  are 
wise  seek  to  distinguish  between  the  beneficial  and  harmful  species 
and  to  protect  the  beneficial  ones. 

Four  groups  of  hawks  are  commonly  met  with  in  California  and 
are  here  treated  in  order  of  estimated  economic  importance.  The 
various  species  of  each  group  have  certain  habits  and  characters  in 
common.     The  groups  with  their  identifying  features  are  as  follows: 

1.  Soaring,  "squirrel"  hawks,  including  rough-leg  or  "chap" 
hawks — beneficial. 

2.  Round- winged,  long-tailed,  "aeroplane"  bird  hawks — harmful. 

3.  Marsh  or  meadow  haunting  hawks — beneficial. 

4.  Long-winged  chasers,  falcons,  "bullet"  hawks — some  harmful, 
others  beneficial. 

The  "soaring"  hawks,  including  the  rough-leg  or  "chap"  hawks 
(so-called  because  their  legs  are  feathered  clear  down  to  the  toes),  are 
represented  by  five  species :  western  red-tail,  Swainson,  red-bellied, 
and  ferruginous  and  American  rough-leg.  All  are  large  hawks,  have 
a  length  of  18  to  25  inches  from  bill  to  tip  of  tail,  and  weigh  from 
IV2  to  3V4  pounds.  In  the  soaring  hawks,  during  flight,  the  length 
(bill  to  tail)  is  less  than  half,  about  42  per  cent,  of  the  spread  of  the 
wings.     These  large  soaring  hawks  are  all  decidedly  beneficial  and 


Circular  236 


COMMON   HAWKS   AND   OWLS    OF    CALIFORNIA 


should  never  be  shot  on  mere  suspicion.  Furthermore,  they  are  all 
protected  by  law.  Investigation  has  shown  that  much  of  the  catching 
of  chickens  and  game  birds,  often  credited  to  them,  is  really  done  by 
the  true  bird  hawks.  The  western  red-tail,  wrongly  called  "hen 
hawk,"  is  the  best  known  representative  of  the  soaring  hawk  group. 
This  hawk  is  resident  in  the  valleys,  oak-covered  foothills,  and  lower 
mountain  ranges  throughout  the  state.  Birds  of  this  group  of  bene- 
ficial hawks  are  often  seen  soaring  in  broad  circles  over  cultivated 
fields.  While  thus  soaring  they  may  be  told  by  their  broad,  not 
pointed,  wings,  slow  flight  and  by  the  spread  tail,  which  is  short  and 
semicircular  in  outline  (see  fig.  1). 


Fig.  1. — Red-tailed  hawk  soaring.  In  flight  this  and  other  beneficial  hawks 
may  be  told*  by  the  short  fan-shaped  tail  and  the  short  body,  the  distance  from  bill 
to  end  of  tail  being  less  than  50  per  cent  of  the  total  spread  of  the  wings. 

The  soaring  hawks  are  notably  noisy  and  habitually  select  exposed 
perches,  such  as  telephone  poles  or  the  dead  tops  of  large  trees.  Also, 
these  large  hawks  usually  choose  commanding  situations  for  their  nest 
sites;  hence  they  are  the  conspicuous  hawks  "potted"  by  the  thought- 
less hunter.  Their  bulky  nests,  composed  of  interlaced  sticks,  firmly 
saddled  in  the  upper  crotches  of  some  large  oak  or  sycamore,  are 
characteristic  features  of  the  landscape  along  our  river  valleys  and 
foothills. 

The  writer  has  examined  over  one  hundred  nests  of  soaring  hawks, 
many  of  which  contained  young,  yet  he  has  never  found  one  contain- 
ing the  remains  of  any  chicken  or  game  bird.  In  one  valley,  twenty- 
two  hawk  nests  were  found  within  a  radius  of  six  miles  near  San 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Onofre,  San  Diego  County.  Eleven  of  these  nests  were  occupied  at 
the  time  by  hawks  or  owls.  The  remains  of  gophers,  ground  squirrels, 
meadow  mice,  young  cotton-tail  rabbits,  and  two  species  of  snakes  were 
found  in  red-tails'  nests;  ground  squirrels  (see  fig.  2)  seemed  to  be 
preferred  above  other  articles  of  diet.  As  a  result  of  their  persistence 
in  catching  these  rodents  the  soaring  hawks  are  often  aptly  called 
' '  squirrel ' '  hawks. 

The  "bird  hawks"  are  represented  by  three  species,  the  sharp- 
shinned  and  Cooper  hawks,  and  goshawk.  These  are  all  quiet  birds, 
in  marked  contrast  to  the  noisy  soaring  hawks.  The  first  two  are  com- 
mon, but  the  goshawk  is  fortunately  rare  in  most  parts  of  California. 
The  bird  hawks  are  decidedly  harmful  and  deserve  no  quarter  since 
they  live  principally  upon  song  and  game  birds  and  poultry.  Instead 
of  perching  in  the  open,  the  bird  hawks  sneak  from  tree  to  tree,  hiding 
in  the  thick  foliage,  and  capture  their  prey  by  stealth,  hidden  approach, 
and  sudden  surprise.  The  best  field  identification  marks  for  these 
harmful  bird  hawks  are  the  short  rounded  wings  and  long  narrow 
tail,  features  which  give  these  birds  when  sailing  a  decided  "aero- 
plane" outline.  In  flight,  all  three  species  flap  their  wings  rapidly 
several  times,  and  then  sail  or  ' '  plane ' '  a  short  distance.  Observations, 
photographs,  and  measurements  show  that  when  hawks  are  flying 
about  directly  overhead  those  which  have  short  tails  and  bodies  and 
widespreading  wings  are  of  the  beneficial  kinds,  while  those  with 
long  tails  and  bodies  and  short  rounded  ivings  are  of  the  harmful 
group.  For  example,  in  the  Swainson  hawk,  which  is  beneficial,  the 
length  averages  40  per  cent  of  the  spread,  while  in  the  Cooper  hawk, 
a  harmful  species,  the  length  is  60  per  cent  of  the  spread.  The  Cooper 
hawk,  a  typical  bird  hawk,  of  medium  size,  14  to  20  inches  in  length, 
is  believed  to  be  the  worst  hawk  in  California,  since  it  is  most  destruc- 
tive to  young  chickens,  the  larger  song  birds,  and  quail.  This  species 
is  resident  over  a  large  portion  of  the  state.  On  account  of  secretive 
habits  and  inconspicuous  nest  a  pair  of  Cooper  hawks  may  raise  a 
brood  of  young  within  200  yards  of  a  farmer's  house  without  his  ever 
discovering  the  nest,  although  young  chickens  may  be  disappearing 
daily.  A  nest  of  this  species  found  by  Mr.  J.  Grinnell  in  the  Santa 
Rosa  Mountains  of  southern  California,  June  27,  1908,  contained  three 
young,  about  one-third  grown.  The  female  had  been  shot  two  days 
previously,  but  the  male  parent  had  not  only  kept  the  young  well 
fed,  but  had  provided  a  surplus  on  the  edge  of  the  nest  consisting  of 
three  flickers,  one  California  jay,  and  one  chipmunk.  At  Escondido 
in  San  Diego  County,  a  male  Cooper  hawk  came  daily  to  the  author's 
ranch   and  carried   off  young  chickens.     The   attacks   came  without 


Circular  236 


COMMON   HAWKS  AND  OWLS   OF   CALIFORNIA 


warning  and  the  hawk  made  his  "getaway"  so  quickly  that  it  was  a 
matter  of  watching  ten  days  before  the  depredations  were  ended  with 
a  shotgun.  Some  innocent  red-tail,  happening  to  be  within  sight  or 
hearing,  thus  might  easily  have  been  blamed  for  the  depredations  of 
the  Cooper  hawk. 


•ft 

Fig.  2. — The  California  ground  or  digger  squirrel  causes  an  estimated  annual 
loss  of  10  million  dollars  in  this  state.  Squirrel  hawks  are  one  of  Nature's  most 
effective  checks  on  these  destructive  rodents. 


The  sharp -shinned  hawk  is  a  miniature  Cooper  hawk  and  is  very 
destructive  to  the  smaller  song  and  insectivorous  birds.  It  is  about 
the  size  of  a  sparrow  hawk,  being  from  10  to  14  inches  in  length  and 
weighing  from  4  to  6  ounces.  Small  as  this  species  is,  individuals 
have  been  seen  to  catch,  kill,  and  try  to  carry  off  a  valley  quail  weigh- 


b  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ing  5%  ounces,  or  practically  as  much  as  the  hawk  itself.  The  Cooper 
and  sharp -shinned  hawks  are  not  protected  by  law  and  may  be  killed 
at  any  time.  In  most  parts  of  California,  the  latter  is  present  chiefly 
or  only  as  a  winter  visitor. 

The  western  goshawk  is  the  third  and  largest  species  of  bird  hawk, 
the  sharp-shinned  being  the  smallest.  This  hawk  is  from  22  to  24y2 
inches  long  and  weighs  2  pounds,  and  is  therefore  large  enough  to 
carry  off  good-sized  chickens  and  grouse.  It  is,  in  fact,  very  destruc- 
tive. The  species  has  been  known  to  breed  in  the  mountains  in  the 
northeastern  part  of  the  state,  but  elsewhere  in  California  it  may  be 
considered  only  a  rare  winter  visitor. 


Fig.  3. — A  prairie  falcon;  a  long-winged  chaser  in  flight. 

The  "meado%v  haunting"  hawks  have  but  one  common  representa- 
tive in  California.  This  bird,  the  marsh  or  "mouse"  hawk,  appears 
to  be  of  large  size,  because  of  its  length,  from  20  to  24  inches,  com- 
bined with  long  pointed  wings.  Adult  individuals,  however,  often 
weigh  less  than  one  pound,  or  about  one-half  as  much  as  other  hawks 
of  the  same  apparent  size.  The  marsh  hawk  beats  back  and  forth 
over  meadow  and  open  grassland  keeping  close  to  the  ground  and 
dipping  down  now  and  then  to  snatch  up  some  small  rodent,  taken 
by  surprise.  In  the  field  this  species  is  easily  told  by  the  white  rump 
patch  and,  at  close  range,  by  the  owl-like  ruff  of  feathers  about  its 
eyes.  This  is  our  only  species  of  hawk  which  habitually  nests  on  the 
ground  in  marshy  places.  This  hawk  rarely  touches  poultry.  Its 
food  consists  largely  of  meadow  mice  and  gophers.  The  wise  farmer 
will  therefore  protect  it  on  his  premises  at  all  times. 


Circular  236 


COMMON  HAWKS  AND  OWLS   OF   CALIFORNIA 


The  falcons,  or  "long-winged  chasers"  (see  fig.  3),  are  represented 
by  four  species :  prairie  falcon,  duck  hawk,  pigeon  hawk,  and  sparrow 
hawk.  The  falcons  can  always  be  told  in  the  hand  by  their  having  a 
tooth-like  projection  near  the  middle  of  each  cutting  edge  of  the 
upper  half  of  the  bill  (see  fig.  4).  In  all  the  other  hawks  this  part 
of  the  bill  is  even,  without  tooth  or  notch  (see  fig.  5). 


Fig.  4. — The  falcons  can  always  be  distinguished  by  the  tooth-like  projection 
on  each  cutting  edge  of  the  upper  half  of  the  bill. 


The  prairie  falcon  and  duck  hawk  are  often  called  "bullet"  hawks 
on  account  of  their  rapid  flight  and  method  of  "stooping"  or  diving 
at  their  prey.  These  "noble"  hawks  are  the  most  sportsmanlike  of 
all  the  birds  of  prey,  since  they  frequently  capture  their  quarry  in 
fair  chase  by  reason  of  their  superior  speed.  The  prairie  falcon 
(see  fig.  6)  has  a  length  of  from  17  to  20  inches,  and  is  found  chiefly 
in  the  semi-arid  interior  valleys;  the  duck  hawk,  slightly  larger 
and  darker,  is  found  more  commonly  along  the  coast.  Both  of  these 
large  falcons  have  conspicuous  black  "mustaches"  or  stripes  on  the 
sides  of  their  heads.  Both  species  nest  in  niches  or  potholes  on  rugged 
cliffs.  No  nest  is  made,  the  eggs  being  laid  on  the  bare  sand  which 
covers  the  bottom  of  the  cavity.  These  large  falcons  do  not  ordinarily 
disturb  poultry  unless  driven  by  extreme  hunger  and  then  their  daring 
and  persistence  usually  proves  their  undoing  since  they  are  apt  to 
linger  around  and  are  easily  shot. 

The  comparatively  rare  pigeon  hawk  and  the  common  sparrow 
hawk  are  approximately  of  the  same  size,  9  to  13  inches  in  length. 
The  pigeon  hawk  is  much  darker  in  color  than  the  sparrow  hawk,  has 
no  black  stripes  on  the  sides  of  the  head,  and  is  only  a  winter  visitor 
in  California.  The  sparrow  hawk  is  resident  and  known  to  nearly 
everyone.     It  is  quite  harmless  but  is  sometimes  confused  with  the 


8 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


sharp-shinned  hawk  and  killed  by  uninformed  people.  There  is  no 
need  of  making  this  mistake,  since  the  sparrow  hawk  has  long  pointed 
wings,  two  black  stripes  on  the  side  of  the  head,  and  a  reddish  back. 
The  sharp-shinned  has  short  rounded  wings,  no  black  stripes  on  side 
of  head,  and  dull  dark  brown  or  slaty  back. 


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Fig.  5. — Head  of  live  red-bellied  haAvk.     In  all  the  hawks  except  the  falcons, 
the  cutting  edge  of  the  bill  is  sharp  but  even,  not  toothed. 


To  sum  up  the  hawks:  Out  of  the  four  groups  which  include  16 
of  the  20  species  of  hawks  found  in  California,  only  one  group  is 
decidedly  harmful.  This  group,  the  bird  hawks,  consists  of  three 
species,  all  of  which  may  be  recognized  by  their  quiet,  stealthy,  sneaky 
habits  and,  in  flight,  by  their  short  round  wings  and  long  tail  which 


Circular  236 


COMMON   HAWKS   AND  OWLS   OF   CALIFORNIA 


give  them  a  decided  "aeroplane"  outline.  The  members  of  this  group 
deserve  no  sympathy.  The  other  13  species  of  hawks  in  California 
are,  with  the  exception  of  one  falcon,  the  duck  hawk,  predominantly 
beneficial  and  should  be  protected.  It  is  a  lamentable  custom  of  many 
hunters  to  shoot  every  hawk  that  they  can,  thinking  that  by  doing  so 


Fig.   6. — An  aggressive  captive  prairie  falcon.     Note   dark  stripe  on   side   of 
head  below  eye,  and  "tear  drop"  spotting  on  breast. 


they  are  rendering  the  community  a  favor,  whereas  in  nine  cases  out 
of  ten  it  is  a  beneficial  hawk  which,  being  most  readily  seen  or  heard, 
is  killed. 

Owls,  working  on  the  night  shift,  take  up  the  work  of  rodent  de- 
struction when  the  hawks  leave  off  in  the  evening.     Song  and  game 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

birds  are  not  abroad  during  the  hours  of  darkness  when  owls  are  most 
active,  hence  these  birds  usually  form  a  very  small  per  cent  of  the 
food  taken  by  owls.  The  common  owls  of  this  state  may  for  con- 
venience be  divided  into  two  groups :  those  that  have  conspicuous 
ear  tufts  or  "horns"  and  those  which,  lacking  these,  appear  "round 
headed."  The  horned,  long-eared,  and  screech  owls  belong  to  the 
first  group,  and  the  barn  and  ground  or  "billy"  owl,  to  the  second 
group.  T&e  so-called  ears  or  horns  are  only  tufts  of  feathers  which 
may  be  erected  or  depressed  at  will  by  the  bird.  The  true  ear  of  an 
owl  is  a  wonderfully  developed  organ  of  hearing  encased  in  the  bony 
structure  of  the  skull  and  its  opening  is  protected  by  a  movable  fringe 
of  stiff  feathers.  The  sense  of  hearing  is  relatively  as  keen  in  the  owl 
as  the  sense  of  sight  in  a  hawk,  so  that  the  term  "owl-eared"  would 
be  just  as  appropriate  as  "hawk-eyed." 

The  homed  or  hoot  owl  is  the  largest  of  all  the  common  owls  in 
California.  It  has  a  length  of  from  18  to  25  inches,  is  of  stocky  build, 
and  weighs  from  2  to  3  pounds.  The  conspicuous  horns  or  ear  tufts, 
and  the  deep  voiced  whoo!  whoo!  ia-whool  so  often  heard  at  night, 
are  the  two  most  striking  characters  of  this  owl. 

The  horned  owl  is,  with  the  possible  exception  of  the  Anna  hum- 
mingbird, the  earliest  nesting  bird  in  California.  Fresh  eggs  have 
been  found  by  J.  B.  Dixon  in  San  Diego  County  on  January  29 
(1911).  Kecords  of  the  nesting  dates  of  a  particular  pair  of  horned 
owls  are  available  for  over  thirteen  years.  Glancing  over  these  records, 
we  find  that  this  pair  nested  in  old  hawks '  nests  five  times,  and  in  the 
other  eight  instances  nested  on  some  rocky  ledge  of  a  steep  hillside 
adjacent.  The  variation  in  nesting  dates  has  been  slight,  January  29 
to  February  14.  In  five  instances  three  eggs,  and  in  eight  cases  two 
eggs  were  laid.  Both  parents  assisted  in  incubation.  The  period  of 
incubation  was  found  to  be  slightly  over  twenty-eight  days.  The  pair 
of  owls  did  considerable  hunting  and  flying  about  in  the  daytime, 
especially  on  cloudy  days. 

The  following  is  an  exact  account  of  food  found  in  the  nest  of  this 
pair  of  owls  covering  a  period  of  two  weeks  when  the  owlets  were 
small :  parts  of  two  brush  rabbits,  three  wood  rats  and  ^Ye  kangaroo 
rats  (see  fig.  7).  Only  on  one  occasion  was  there  any  indication  of 
these  owls  feeding  on  other  birds,  that  being  a  small  bunch  of  quail 
feathers  at  the  base  of  the  cliff.  If  birds  or  poultry  had  been  taken 
to  any  considerable  extent,  some  feathers  would  certainly  have  been 
found  about  the  nest.  Notebook  records  of  over  50  nests  of  horned 
owls  examined,  containing  eggs  or  young,  fail  to  show  any  trace  of 
poultry  having  been  taken.     The  writer  therefore  believes  that  the 


Circular  236 


COMMON  HAWKS  AND  OWLS   OF   CALIFORNIA 


11 


poultry-stealing  proclivities  of  this  owl,  in  California,  have  been 
grossly  over-estimated,  to  say  the  least.  The  horned  owl  is  an  im- 
portant rodent  destroyer  in  California  and  should  be  given  legal  pro- 
tection instead  of  being  classed  as  an  outlaw. 

The  long -eared  owl  has  a  length  of  from  13  to  16  inches.  As  indi- 
cated by  its  name,  the  ear  tufts  in  this  species  are  very  well  developed 
and  this  feature,  together  with  the  medium  size  of  the  bird,  affords 
the  best  field  identification  mark.     Although  this  owl  may  be  found 


Fig.  7. — The  horned  owl  is  one  of  the  best  rodent  destroyers  in  California.  This 
is  evidenced  by  the  remains  of  a  wood  rat  in  the  nest  behind  the  two  white  downy 
young. 


in  suitable  localities  over  most  of  the  state,  it  is  a  species  rarely  seen 
during  daylight  hours,  for  it  spends  the  day  hidden  away  in  the 
densest  cover  that  it  can  find.  Like  the  horned  owl,  the  present 
species  preempts  the  nests  of  other  birds  or  animals  and  rarely  if  ever 
builds  a  nest  for  itself.  In  southern  California  the  long-eared  owl 
commonly  nests  on  top  of  old  wood  rat  nests,  which  in  that  region  are 
often  built  in  oak  trees  from  10  to  30  feet  above  the  ground.  Nests 
of  crows  and  magpies  are  also  appropriated  by  these  owls  (see  fig.  8). 
At  Mono  Lake  in  May,  1916,  the  writer  found  six  pairs  of  long-eared 
owls  all  nesting  in  magpie  nests.  The  owls  nested  earlier  than  the 
magpies  and  apparently  had  first  choice  of  the  old  nests  available, 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


since  in  nearly  every  instance  a  new  nest  was  built  nearby  by  the  mag- 
pies. From  3  to  7  white  eggs  are  laid  the  last  of  April  or  first  of 
May  (see  fig.  9).  Both  parents  are  valiant  defenders  of  their  nest. 
In  the  case  of  one  pair,  the  female  stood  boldly  on  the  rim  of  the  nest, 
fluffed  out  her  feathers,  depressed  her  ear  tufts,  and  glared  at  the 
intruder.  The  male  bird  flitted  about  the  nest,  hooting  excitedly  and 
mewing  like  a  cat.  As  soon  as  the  observer  set  up  his  camera  and 
put  his  head  under  the  focusing  cloth,  he  was  taken  by  surprise  by 
the  male  owl,  which  swooped  noiselessly  down  and  started  to  dance 
a  jig,  with  his  sharp  claws  working  furiously,  on  the  top  of  the 
photographer's  head. 


Fig.  8. — A  brooding  long-eared  oavI.  Note  the  long  ear  tufts  which  give  the 
bird  its  name.  This  owl  is  an  excellent  mouser  and  merits  the  legal  protection 
that  has  been  given  it. 

The  owlets  when  hatched  were  covered  with  fluffy  white  thistle- 
down-like feathers.  Ten  days  later,  bluish  pin  feathers  began  to 
appear  and  the  owlets  developed  tremendous  appetites,  so  that  the 
parents  started  hunting  as  soon  as  the  sun  was  down  in  order  to 
keep  their  hungry  youngsters  fed.  As  the  owlets  grew  older  they 
began  to  edge  away  from  the  nest,  and  long  before  they  were  able 
to  fly  they  hopped  about  freely  from  limb  to  limb  in  the  dense  willow 
thickets  (see  fig.  10).  Mice  were  abundant  on  the  sandy  sage-covered 
flats  and  in  the  grassy  meadows  near  the  owls'  home.  Remains  of 
white-footed,  meadow,  and  pocket  mice  were  found  about  the  nest,  but 
no  bird  remains  were  ever  discovered  there.  The  long-eared  owl  lives 
almost  exclusively  on  the  smaller  mice  and  is  therefore  one  of  the 
most  beneficial  birds  in  the  state. 


Circular  236 


COMMON   HAWKS  AND  OWLS   OF   CALIFORNIA 


13 


Last,  and  least  of  the  eared  owls,  comes  the  little  screech  owl  (see 
fig.  11),  which,  by  the  way,  does  not  ordinarily  "screech"  but  gives 
a  low,  mellow,  quavering  call  toock,  toock,  toock,  tut-tut-tu  tu  tu  tu, 
repeated  rapidly  toward  the  end.  This  pocket  edition  of  the  horned 
owl  is  from  7%  to  10  inches  long  and  is  small  enough  to  enter  easily 
a  flicker  hole.  In  such  cavities,  they  lay  their  4  or  5  round  white 
eggs.  Normally,  this  species  feeds  upon  mice  and  the  larger  insects. 
It  is  commonly  found  about  farms,  living  in  trees  near  the  farm  build- 
ings.    The  screech  owl  seems  to  seek  out  human  habitations,  perhaps 


jl J;  ^fty *  ?    \  « »  ^  iA^7?*W-->. 

^^tMll  -?N 

J^hBHmX       Iff  i^m^'-^B  pjBLvrPjf'i^^ 

-&  Jp.  vimjtt  4^S&^^l^J^^Brs^ 

'*»rif™  \\wdh  *Ww't*     - 

Fig.  9. — Five  eggs  of  long-eared  owl  in  an  old  magpies'  nest.  This  owl  pre- 
empts the  nests  of  other  birds  and  mammals,  rarely  building  a  nest  for  itself. 

being  influenced  by  the  abundance  of  mice  usually  to  be  found  there. 
Individuals  sometimes  take  up  quarters  in  bird  boxes  and  may  drive 
out  or  even  destroy  the  other  bird  tenants ;  but,  taking  it  by  and  large, 
they  are  decidedly  beneficial  and  should  not  be  killed. 

Taking  up  the  round-headed  owls,  or  those  which  lack  ear  tufts, 
we  have  the  medium-sized  barn  or  monkey-faced  owl  and  the  little 
ground  or  "billy"  owl.  The  barn  owl  has  a  length  of  from  15  to  18 
inches  and  is  often  described  as  a  white  or  golden  owl.  This  species, 
as  its  name  implies,  is  commonly  found  living  in  barns,  tank  houses,, 
or  other  outbuildings.  The  food  of  the  barn  owl,  especially  in  alfalfa 
sections,  consists  principally  of  pocket  gophers  and  mice.    On  May  13, 


14 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


1914,  near  Mendota,  Fresno  County,  Mr.  J.  G.  Tyler  found  two  pairs 
of  barn  owls  nesting  in  an  old  tank  house.  "One  nest  was  placed  in 
the  tank  on  the  bones,  fur,  pellets,  and  refuse  that  had  accumulated 
to  a  depth  of  several  inches.  One  bird  was  perched  on  a  beam  over- 
head asleep,  while  his  mate  occupied  the  nest,  which  contained  four 
very  small  birds  and  six  eggs.  Scattered  about  on  the  floor  were  five 
pocket  gophers  (Thomomys) ,  five  kangaroo  rats  (Perodipus),  one 
pocket  mouse  (Perognathus) ,  and  two  white-footed  mice  (Peromys- 
cus),  all  of  which  were  in  good  condition  and  undoubtedly  of  the 
previous  night's  catch.    Besides  these,  there  were  partly  eaten  remains 


Fig.  10. — As  the  owlets  grew  older  they  began  to  edge  away  from  the  nest 
and  long  before  they  were  able  to  fly  they  hopped  about  from  limb  to  limb  in 
the  dense  willow  thickets. 


and  fresh  skeletons  of  several  more.  If  the  thoughtless  persons  who 
so  relentlessly  destroy  this  owl  on  account  of  its  supposed  fondness 
for  chickens  and  pigeons  would  take  the  trouble  to  keep  watch  of  a 
nest  site  through  one  season,  the  most  ignorant  among  them  could 
hardly  fail  to  realize  that  they  are  working  against  their  own  best 
interests  whenever  they  kill  a  barn  owl."     (See  front  cover.) 

The  ground  owls  are  probably  known  by  sight  to  more  people  in 
California  than  is  any  other  species  of  owl  in  the  state.  This  is  largely 
due  to  their  habit  of  living  in  open  country  and  to  their  being  abroad 
in  the  daytime.  Their  predilection  for  perching  on  fence  posts  and 
telephone  poles  (see  fig.  12)  and  their  curious  manner  of  watching 
passers-by  bring  them  to  the  attention  of  the  people  traveling  along 
the  highways.    To  schoolboy  and  Argonaut  alike,  this  owl  is  affection- 


Circular  236 


COMMON  HAWKS  AND  OWLS   OF   CALIFORNIA 


15 


ately  known  as  " billy"  owl.  This  is  the  only  one  of  our  owls  that 
habitually  nests  underground.  Old  burrows  of  ground  squirrels  are 
usually  chosen,  and  the  nest,  made  almost  always  of  finely  broken 
horse  manure,  is  placed  at  the  end  of  the  burrow.    It  is  believed  that, 


Fig.  11. — The  screech  owl,  a  pocket  edition  of  the  horned  owl,  is  the  smallest 
of  the  ' '  eared ' '  owls  and  often  lives  in  nicker  holes  in  trees  about  farm  buildings 
where  it  catches  many  mice. 

in  addition  to  serving  as  a  soft  nest  material,  the  manure,  especially 
when  the  ground  is  damp,  also  serves  as  an  incubator,  much  as  it  does 
in  the  ordinary  hotbed  used  in  sprouting  sweet  potatoes.    These  little 


16  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  12. — The  ground  owl  or  "billy"  owl  is  probably  known  by  sight  to  more 
people  than  any  other  owl  in  the  state.  This  owl  feeds  chiefly  on  insects  such  as 
grasshoppers  and  crickets  and  should  be  protected  at  all  times. 


Circular  236  common  hawks  and  owls  of  California  17 

owls  are  harmless.  They  live  for  the  most  part  on  grasshoppers  and 
crickets.  They  hunt  mainly  in  the  evenings  and  at  night,  bnt  are 
often  seen  catching  grasshoppers  in  the  daytime.  Judged  by  stomach 
contents,  and  food  found  in  owl  pellets  and  in  nests  containing  young 
owls,  all  the  species  of  owls  commonly  found  in  California  do  more 
good  than  harm  and  should  be  protected  at  all  times. 

Of  the  four  groups  of  hawks  found  in  the  state,  two  groups,  the 
squirrel  hawks  and  the  mouse  hawks,  are  beneficial.  One  group,  the 
bird  hawks,  is  harmful ;  while  the  fourth  group,  the  falcons,  consists 
of  some  species  that  are  beneficial  and  some  that  are  harmful.  All 
the  common  species  of  owls  are  believed  to  be  beneficial  to  man's 
interests. 

The  far-sighted  rancher  will  protect  the  many  beneficial  bird  ten- 
ants on  his  lands  and  will  seek  to  destroy  only  the  few  harmful  species. 

Transmitted  August  11,  1920. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


BULLETINS 


No. 
185. 

241. 
246. 
251. 

253. 

261. 
262. 

263. 
266. 

267. 
268. 
270. 


271. 
273. 

275. 

276. 
278. 
279. 
280. 

282. 

283. 

285. 
286. 
287. 
294. 
297. 
298. 


No. 

Report  of  Progress  in  Cereal  Investiga-  299. 

tions.  300. 

Vine  Pruning  in  California,  Part  I.  304. 
Vine  Pruning  in  California,  Part  II. 

Utilization  of  the  Nitrogen  and  Organic  308. 

Matter    in    Septic    and    Imhoff    Tank 

Sludges. 

Irrigation    and    Soil    Conditions    in    the  309. 

Sier/a  Nevada  Foothills,  California. 

Melaxuma  of  the  Walnut,  "Juglans  regia."  310. 

Citrus    Diseases    of    Florida    and    Cuba  312. 

Compared  with  Those  of  California.  313. 

Size  Grades  for  Ripe  Olives.  316. 

A  Spotting  of  Citrus  Fruits  Due  to  the  317. 

Action  of  Oil  Liberated  from  the  Rind.  318. 

Experiments  with  Stocks  for  Citrus.  320. 

Growing  and  Grafting  Olive  Seedlings.  321. 

A  Comparison  of  Annual  Cropping,  Bi-  323. 

ennial   Cropping,    and    Green    Manures 

on  the  Yield  of  Wheat.  324. 
Feeding  Dairy  Calves  in  California. 

Preliminary  Report  on  Kearney  Vineyard  325. 

Experimental  Drain. 
The  Cultivation  of  Belladonna  in  Cali- 
fornia. 328. 
The  Pomegranate.  330. 
Grain  Sorghums.  331. 
Irrigation  of  Rice  in  California.  332. 
Irrigation  of  Alfalfa  in  the  Sacramento  334. 

Valley. 

Trials  with   California   Silage   Crops   for  335. 

Dairy  Cows. 

The  Olive  Insects  of  California.  336. 
The  Milk  Goat  in  California. 

Commercial  Fertilizers.  337. 

Vinegar  from  Waste  Fruits.  339. 
Bean  Culture  in  California. 

The  Almond  in  California.  340. 
Seedless  Raisin  Grapes. 


The  Use  of  Lumber  on  California  Farms. 

Commercial  Fertilizers. 

A  Study  on  the  Effects  of  Freezes  on 
Citrus  in  California. 

I.  Fumigation  with  Liquid  Hydrocyanic 
Acid.  II.  Physical  and  Chemical  Pro- 
perties of  Liquid  Hydrocyanic  Acid. 

I.  The  Carob  in  California.  II.  Nutritive 
Value  of  the  Carob  Bean. 

Plum  Pollination. 

Mariout  Barley. 

Pruning  Young  Deciduous  Fruit  Trees. 

The  Kaki  or  Oriental  Persimmon. 

Selections  of  Stocks  in  Citrus  Propagation. 

The  Effects  of  Alkali  on  Citrus  Trees. 

Control  of  the  Coyote  in  California. 

Commercial  Production  of  Grape  Syrup. 

Heavy  vs.  Light  Grain  Feeding  for  Dairy 
Cows. 

Storage  of  Perishable  Fruit  at  Freezing 
Temperatures. 

Rice  Irrigation  Measurements  and  Ex- 
periments in  Sacramento  Valley,  1914- 
1919. 

Prune  Growing  in  California. 

Dehydration  of  Fruits. 

Phylloxera- Resistant  Stocks. 

Walnut  Culture  in  California. 

Preliminary  Volume  Tables  for  Second- 
Growth  Redwoods. 

Cocoanut  Meal  as  a  Feed  for  Dairy  Cows 
and  Other  Livestock. 

The  Preparation  of  Nicotine  Dust  as  an 
Insecticide. 

Some  Factors  of  Dehydrater  Efficiency. 

The  Relative  Cost  of  Making  Logs  from 
Small  and  Large  Timber. 

Control  of  the  Pocket  Gopher  in  California. 


CIRCULARS 


No.  No. 

70.  Observations    on    the    Status    of    Corn  165. 

Growing  in  California. 

82.  The  Common  Ground  Squirrels  of  Cali-  166. 

fornia.  167. 

87.  Alfalfa.  169. 

110.  Green  Manuring  in  California.  170. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils.  172. 

113.  Correspondence  Courses  in  Agriculture.  173. 

115.  Grafting  Vinifera  Vineyards.  174. 

126.  Spraying  for  the  Grape  Leaf  Hopper.  175. 

127.  House  Fumigation. 

128.  Insecticide  Formulas.  176. 

129.  The  Control  of  Citrus  Insects. 

130.  Cabbage  Growing  in  California.  177. 
135.  Official  Tests  of  Dairy  Cows.  178. 
138.  The  Silo  in  California  Agriculture.  179. 
144.  Oidium  or  Powdery  Mildew  of  the  Vine. 

148.  "Lungworms."  181. 

151.  Feeding  and  Management  of  Hogs.  182. 

152.  Some  Observations  on  the  Bulk  Handling 

of  Grain  in  California.  183. 

153.  Announcement    of    the    California    State  184. 

Dairy  Cow  Competition,  1916-18.  188. 

154.  Irrigation    Practice    in    Growing    Small  189. 

Fruits  in  California.  190. 

155.  Bovine  Tuberculosis.  193. 

157.  Control  of  the  Pear  Scab.  198. 

158.  Home  and  Farm  Canning.  201. 

159.  Agriculture  in  the  Imperial  Valley.  202. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in  California.  203. 
164.  Small  Fruit  Culture  in  California.  205. 


Fundamentals    of    Sugar    Beet    Culture 

under  California  Conditions. 
The  County  Farm  Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
The  1918  Grain  Crop. 
Fertilizing  California  Soils  for  the   1918 

Crop. 
Wheat  Culture. 

The  Construction  of  the  Wood-Hoop  Silo. 
Farm  Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution  of  Milk. 
Hog  Cholera  Prevention  and  the  Serum 

Treatment. 
Grain  Sorghums. 

The  Packing  of  Apples  in  California. 
Factors  of  Importance  in  Producing  Milk 

of  Low  Bacterial  Count. 
Control  of  the  California  Ground  Squirrel. 
Extending  the  Area  of  Irrigated  Wheat  in 

California  for  1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Lambing  Sheds. 
Winter  Forage  Crops. 
Agriculture  Clubs  in  California. 
A  Study  of  Farm  Labor  in  California. 
Syrup  from  Sweet  Sorghum. 
Helpful  Hints  to  Hog  Raisers. 
County  Organizations  for  Rural  Fire  Con- 
trol. 
Peat  as  a  Manure  Substitute. 
Blackleg. 


CIRCULARS— Continued 


No. 

206.  Jack  Cheese. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.  Salvaging  Rain-Damaged  Prunes. 

214.  Seed    Treatment   for   the   Prevention   of 

Cereal  Smuts. 

215.  Feeding  Dairy  Cows  in  California. 

217.  Methods    for    Marketing    Vegetables    in 

California. 

218.  Advanced  Registry  Testing  of  Dairy  Cows. 

219.  The  Present  Status  of  Alkali. 

220.  Unfermented  Fruit  Juices. 

221.  How  California  is  Helping  People  Own 

Farms  and  Rural  Homes. 

223.  The  Pear  Thrips. 

224.  Control  of  the  Brown  Apricot  Scale  and 

the   Italian   Pear   Scale   on   Deciduous 
Fruit  Trees. 


No. 

225.  Propagation  of  Vines. 

227.  Plant  Diseases  and  Pest  Control. 

228.  Vineyard  Irrigation  in  Arid  Climates. 

229.  Cordon  Pruning. 

230.  Testing  Milk,  Cream,  and  Skim  Milk  for 

Butterfat. 

231.  The  Home  Vineyard. 

232.  Harvesting     and      Handling     California 
Cherries  for  Eastern  Shipment. 

Artificial  Incubation. 

Winter  Injury  to  Young  Walnut  Trees 
During  1921-22. 

Soil  Analysis  and  Soil  and  Plant  Inter- 
relations. 

The  Common  Hawks  and  Owls  of  Cali- 
fornia from  the  Standpoint  of  the 
Rancher. 

Directions  for  the  Tanning  and  Dressing 
of  Furs. 


233. 
234. 


235. 
236. 


237. 


